Extracting the mean profile is based on the really nice paper by Chu et al (2010).
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## toHTML
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## filter, lag
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## Call:
## lm(formula = twist ~ x, data = subset(dframe, between(x, 220,
## 600)))
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## Residuals:
## Min 1Q Median 3Q Max
## -8.0459 -1.1544 -0.1613 0.8461 9.4853
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## Coefficients:
## Estimate Std. Error t value Pr(>|t|)
## (Intercept) 803.959580 0.465478 1727.2 <2e-16 ***
## x -0.127593 0.001096 -116.4 <2e-16 ***
## ---
## Signif. codes: 0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
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## Residual standard error: 1.884 on 242 degrees of freedom
## Multiple R-squared: 0.9825, Adjusted R-squared: 0.9824
## F-statistic: 1.355e+04 on 1 and 242 DF, p-value: < 2.2e-16
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in black: average of all, in blue average based on profiles below 500, in green average based on profiles below 300, in red profile at 100.